The attacked occurred Monday in Tapachula, Chiapas, after one of the policemen hit the bees' hive with a bullet, local police officer Miguel Serrano said Tuesday. At least 10 of the 70 officers stung were in serious condition, he said.

"We tried as hard as we could, but we weren't able to avoid getting stung," Serrano said. "Some of us hit the ground, but that didn't help."

"It was really bad. I haven't seen anything like it, even in the movies," he said.

Africanized bees, a fierce hybrid strain sometimes referred to as "killer bees," are the result of an experiment to increase honey production in Brazil. A swarm escaped a lab in 1957 and began heading north.